<論文>有機溶媒中でのPseudomonas cepaciaリパーゼ触媒によるトリブチリルグリセリンと 2-アルカノールとのエステル交換におけるエナンチオ選択性

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Pseudomonas cepacia lipase (PCL) catalyzed transesterification between tributyrylglycerol (1) and 2-alkanol (2) to give (R)-1-methylalkyl butyrate (3) was studied using various organic solvents. The resolution data fit the kinetic resolution format of the reverse type of reaction. The enantioselectivity expressed as log E (where E is the enantiomeric ratio) showed a rough negative correlation with the solvent hydrophobicity log P (P is a partition coefficient of a given solvent between octanol and water) and inverse of the dielectric constant (D) except bulky solvents such as cyclohexane, carbon tetrachloride and dioxane, in which the log E values were smaller than those expected from log P and 10/D. The log E against log P and 10/D plots varied according to the structure [carbon number (CN)] of (2). The E value was minimal at CN=8 and 10. The initial rate constant (k/s^<-1> mg^<-1>) was measured for (R)- and (S)-2-octanols [(R)-and (S)-(2b)]. The rate (log k) showed a rough positive correlation with log P, but was essentially independent of D except bulky solvents and dilsopropyl ether. The slope of log k against log P plot for (R)-(2b) was less than for (S)-(2b). The effect of the reaction temperature (T) on the enantioselectivity was also studied for PCL catalyzed transesterification with 2-octanol (2b) using eight kinds of solvents at 10-70℃. The log E agaist log P plot was veried by T. The enantioselectivity increased with T for the reaction in the bulky solvents, was independent of T in heptane, decreased in the other solvents. Activation parameters (⊿⊿H^=⃥ and ⊿⊿S^=⃥) were determined using a linear correlation between ⊿⊿G^=⃥(-RT ln E) and T. The ⊿⊿H^=⃥ values were negative for the reactiond in the bulky solvents and positive in the others, and the ⊿⊿S^=⃥ values in the former were larger than those in the latter. From the above observations, it was demonstrated that the enantiselectivity was affected by a combination of the nature of solvent, the structures of substrate (2) and solvent, and the reaction temperature. A plausible active site model of PCL for the transesterification was proposed and discussed.
北海道東海大学の論文
2000-03-25

<論文>有機溶媒中でのPseudomonas cepaciaリパーゼ触媒によるトリブチリルグリセリンと 2-アルカノールとのエステル交換におけるエナンチオ選択性

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<論文>有機溶媒中でのPseudomonas cepaciaリパーゼ触媒によるトリブチリル グリセリンと 2-アルカノールとのエステル交換におけるエナンチオ選択性

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<論文>有機溶媒中でのPseudomonas cepaciaリパーゼ触媒によるトリブチリルグリセリンと 2-アルカノールとのエステル交換におけるエナンチオ選択性